Tree-Crop Interactions
- 1. Frédéric Baudron CIMMYT Ethiopia f.baudron@cgiar.org Agroforestry & Food Security: Assessing the Direct Effects of Trees on Annual Food Crops
- 2. Challenges faced by Annual Food Crop Production Water scarcity Nutrient scarcity – N, P Climate change Pests and diseases Energy scarcity – Labour, ADP, fuel Slow yield gains – Yield gap – Land scarcity – Undernourished people (Water scarcity in 2050, from Wallace, 2000)(from Cairns et al., 2012) (from FAO, 2009)
- 3. A Question of Efficiency? Only 10-30% of water is used by the crop (Wallace, 2000) Only 20-50% of N ferilizers applied is used by cereal crops (Cassman, 2002) Less than 0.1% of pesticides applied reach their pest target (Pimentel, 1995) Management response: Precision agriculture Genetic response Management response: Exploiting positive interactions between species
- 4. (from Cox et al., 2006) An Example of Genetic Response: Developing Perennial Grain Crops
- 5. Precision Agriculture: when, where, how much?
- 6. 1.When does it occur? 2.What are the mechanisms? 3.How to maximize it? Tree - Annual Food Crop facilitation
- 7. Increasing Water Availability The problem: high water loss through runoff, evaporation and deep drainage; shallow root distribution of annuals Reduced evaporation (from Ong et al., 2000) Increased soil water (from Joffre and Rambal, 1993) Hydraulic lift (from Emerman and Dawson, 1996)
- 8. N Fixation and Recycling The problem: production of N fertilizers dependant on fossile energy; highly mobile nutrient,
- 9. P Mobilization & Acquisition The problem: poorly mobile nutrient, mainly in non-available forms in the soil (from Cox et al., 2006) Exudation of organic acids by proteoid roots of e.g. Grevillea robusta (Watt & Evans, 1999) Ectomycorrhizae of e.g. Caesalpinioideae (Högberg, 1992)
- 10. Heat and water stress (from Ong et al., 2000)
- 11. Pest control Rodents: 0.1-0.5 t/ha of field damage in Tigray (Yonas et al., 2010) (from Koh, 2008)
- 12. Interactions Effect of water availability on heat stress of maize (from Lobel et al., 2011)Effect of nutrient application on water productivity (from Penning de Vries and Ditèye, 1991)
- 13. Minimizing Competition Tree species selection – Phenology – Pattern of root activity – Plasticity of the root system Management – Spacing – Supply of limiting factors – Shoot pruning – Tillage (from Burges et al., 1998) (from Schroth et al., 1995)
- 14. (Gc × Gt) × E × M Gc: Diversity of maize varieties – Productivity (e.g. land, water) – Resistance or sensitivity to e.g. heat, drought, low N, pests & diseases Gt: Diversity of tree species – Morphology (above and below ground) – Phenology (inverse or not) E: Diversity of environments – Climates (semi-arid vs. sub-humid) – Soils (N limited vs. P limited) M: Diversity of management options – Geometry – Fertilization – No-till vs. Ploughing 0% 20% 40% 60% 80% 100% 0 100 1000 3000 Waterusebysorghum Surface mulch (kg DM ha-1) Transpiration Runoff Soil evaporation Drainage (from Baudron et al., in prep)
- 15. What to measure (near and away from trees)? Environmental parameters – Radiation and temperature – Soil water content – N and P balance Productivity – Crop yield – Biomass production (crop & trees) Crop stress indicators – NDVI – Canopy temperature Crop damage inside and outside bird- exclosures Fate of biocides - phytoremediation
- 16. Conclusion: Answering Practical Questions for Maize Farmers What happens near trees? What to plant near trees? What management is needed near trees?
- 17. Thank you!